By Ishan Khurana, Lukas Kikuchi and Will Stronge

May 7 2020

Lockdown appears to be working, but now is not the time to go back to business as usual.

Should Government ease lockdown, another peak is likely: the rate of COVID-19 deaths is dependent on policy and does not follow a 'natural' arc.

Worryingly, there are thousands of excess deaths in care homes not being reported as COVID-related. This could represent insufficient testing or an increase in individuals not going to hospital due to a number of possible reasons.

New ONS figures have indicated a possible stagnation in the rate of increase of excess deaths (driven by the COVID-19 virus) in England and Wales. This appears to support the conclusion that lockdown is helping stabilise the impacts of the virus.

Autonomy’s analysis of available ONS data on all excess deaths during this pandemic reveals key messages – and warnings – for government, as it contemplates lockdown easing. Each of the following figures builds the picture of the COVID-19 mortality numbers and categorises where these deaths are being registered.

We believe it is important to be entirely transparent when approaching these questions, and so have published our method here and links to the data sources in a box at the bottom of this page.

First priority:

The aim of every government in the world today ought to be to keep the reproductive ratio of the COVID-19 virus below 1. Estimates suggest that outside of lockdown conditions the virus has a reproductive ratio of between 1.4 – 5.7 (see drop down box below). That is to say, for every person who has the virus, they are likely to pass it on to between 1.4 and 5.7 others if lockdown conditions are not in place. This has clear and obvious implications for the Government’s next course of action, given that there is yet to exist a successful vaccine for COVID-19. Existing studies suggest that short lockdown periods are not sufficient to prevent a resurgence, and the UK should take heed of this evidence.

By considering the UK weekly mortality rates from between 2015 to 2019, we use the averaged weekly mortality rate given by the ONS. This rate can be used as a baseline for what mortality figures would have looked like in the absence of the COVID19 virus. We then subtracted these rates from the corresponding ONS weekly mortality rates for 2020. These are known as the excess death rates, which have been previously reported on here and here.

Herd immunity is reached when a large enough proportion of the population is immune (either recovered or vaccinated), where the immunized serve as a buffer, lowering the probability of secondary infections.

The theoretical herd immunity criterion is

$$
h = \frac{R_0 - 1}{R_0}
$$

where \(R_0\) is the basic reproductive ratio, which is the number of secondary infections produced by a typical case of an infection in a population where everyone is susceptible. Herd immunity is reached when \(h \times N\) number of people have been infected and recovered from the virus, where \(N\) is the population of the country.

As the basic reproductive ratio is both a function of the inherent infectivity of the pathogen, as well as the social contact structure of the susceptibles, \(R_0\) has a lower value during lock-down. This is why there is often talk about "keeping \(R_0\) below \(1\)" in the media.

Estimates for \(R_0\) of the COVID-19 virus vary from \(1.4\) to \(5.7\) [Refs: 1-4], outside of a lock-down. Using the conservative estimate of \(R_0 = 1.4\), we can estimate the herd immunity criterion to be \(h \sim 28.7\%\). This would mean approximately \(19\) million of the UK's \(66.65\) million inhabitants would have to be infected for herd immunity to be reached. This is a lower-bound.

Current estimates from SAGE suggest that \(4\%\) of the population have been infected with the coronavirus as of the 27th of April [Ref: 5]. Based on the previous calculation, this would leave us with an estimated \(16\) million additional infections required for herd immunity to be reached, in the absence of lock-down. These would very likely occur on a time-scale before a vaccine could be found.

It should be noted that pandemics are inherently difficult to predict mathematically. Herd-immunity calculations of the kind written above give a good picture of the general scale of the pandemic, but the figures mentioned are ball-park at best.

Figure 3e: Percentage of total excess deaths by category

+ Lockdown appears to be working, but we’ve only just started our fight with the virus.

+ Care home deaths reported as COVID-related have been outnumbered by other excess deaths in these places. This could represent insufficient testing or an increase in individuals not going to hospital due to a number of possible reasons.

+ Excess care home deaths are broadly concentrated in the North.

+ Another peak in excess deaths is likely, should Government ease lockdown: the arc of COVID-19 deaths is not natural, but dependent on policy.

Figure 1: All deaths recorded since March 13, 2020 in England and Wales

Figure 1 shows all deaths recorded between March 13th and April 24th in 2020. This includes ‘expected’ weekly deaths – the number of deaths we would expect in comparison to prior years.

The peak (10th April) of total weekly deaths from all causes was 20,866.

Figure 2: All weekly, expected and excess deaths since March 13, 2020

As can be seen in figure 2, excess deaths – both the rate and overall, cumulative numbers – peaked around the date of 8th April, as reported in the data from 10th April. This would support the thesis that lockdown measures are working to stabilise mortality rates. The short black lines on each bar represent the margin of error of expected deaths.

Excess deaths from the week beginning 13th March to week ending 24th April amounted to 35,068 (± 1650).

Excess deaths at the 10th April peak amounted to 10,606 (± 246), amounting to just over half of all recorded deaths for that week.

But ‘peak’ can only be a tentative claim, as more time is needed before we can be sure, and any further peaks are largely dependent on government action (e.g. easing lockdown).

Figure 3: Weekly, excess deaths reported in hospitals

As Figure 3 above and 3a below show, the rate of weekly reported hospital deaths have been in decline since the data reported on 10th April.

The peak of reported hospital deaths (10th April) was 5,897.

Figure 3a: Weekly, COVID-related hospital deaths as a proportion of total excess deaths

However, hospital reported deaths makes up 58% of total excess deaths across the period. As only one part of the total excess deaths in this period, hospital reported deaths are an increasingly insufficient metric by which to gauge weekly death rates related to COVID-19, and therefore should not be used as a justification to slacken lockdown.

Figure 3b: Weekly, excess deaths reported in care homes

Figure 3b shows which of the excess deaths beyond reported hospital deaths were recorded in care homes. These are marked in green.

Excess care home deaths make up 20% of total excess deaths over the whole study period.

Although the ONS is reported to have said that the daily death rate ‘appears to be decreasing’ in care homes, this can only be a very provisional claim. The ONS recommend caution however, given the delay in the registration of deaths.

Figure 3c: Weekly, excess deaths reported in care homes as a percentage of total excess deaths

Figure 3c shows that care home deaths are growing as a proportion of total excess deaths, with the data from 24th April revealing that they make up over 30% of total excess deaths for that week.

Figure 3d: Total weekly deaths broken down by category

In Figure 3d we’ve displayed the total weekly deaths and have broken them down into their categories.

The light blue represents the COVID-related deaths confirmed to have been registered in other locations aside from hospitals or care homes; this includes locations such as hospices, private homes and community establishments. Excess (COVID) deaths in ‘all other locations’ makes up 5% of total excess of the whole period.

Any remaining yellow represents excess deaths that have not been reported as directly related to COVID-19 (approx. 6,200 deaths).

Figure 3e: Percentage of total excess deaths by category

In Figure 3e we plot each category as a percentage of overall excess deaths across the period.

Hospital recorded deaths are in decline from the 10th April data report onwards, whilst reported care home COVID-related deaths have been increasing their proportion of the total excess.

In Figure 3f we have plotted total excess deaths that have been reported in care homes and demarcated the amount that have been reported as being COVID-related.

It should be noted that there is a significant excess beyond those reported as COVID-related. Over the past few weeks, this ostensibly non-COVID-related ‘excess’ has made up the majority of care home excess deaths. These ‘other’ deaths are at levels far above the 5 year average, indicating something remarkable is going on. It could represent:

a) That there hasn’t been enough testing that would discover higher levels of COVID infection (corroborating anecdotal evidence – as reported by Reuters).

b) That people in care homes are not going to hospital to pass away, due to a number of possible factors.

In Figure 4 we have plotted the weekly excess deaths in care homes at the local authority level for England and Wales. You can toggle different dates to see the differences between weeks in our chosen period.

If you would like to zoom in to inspect a particular local authority, toggle the zoom box and then scroll and hover your mouse over the location. By clicking through the dates, we can see the stark contrast – representing a significant increase in excess deaths – across the month of April.

County Durham is the worst hit local authority in England and Wales for excess care home deaths. It has seen 133 COVID-related deaths in care homes in April.

Other local authorities were not far behind:

Sheffield has seen 126 COVID-related deaths in care homes in April.

Leeds has seen 110 COVID-related deaths in care homes in April.

Birmingham has seen 105 COVID-related deaths in care homes in April.

Some local authorities saw increases in the weekly excess deaths in care homes

By 24th April, the number of care home COVID-related deaths in Mid Sussex more than doubled to 22 up from 9 the previous week.

Leeds recorded a 27% increase in COVID-related deaths in care homes with 55 deaths up from 40 the previous week.

In Salford, excess deaths appeared to be going down: 13 were recorded in the week ending 10th April, down from 27 the previous week. However, it then saw an increase in excess deaths in the week ending 24th of April with 19 deaths recorded.

Other local authorities saw decreases in the weekly excess deaths in care homes

Liverpool recorded 26% fewer deaths in the week ending 24th of April compared with the previous week, with 31 deaths down from 42.

Cardiff recorded 30% fewer deaths in the week ending 24th of April compared with the previous week, with 21 deaths down from 30.

Note and data sources

Death registrations and occurrences by local authority and health board: Here.

We used excess deaths related to all causes of mortality, as this is widely recognised as the best measure of the mortality impact of Covid-19. This is because it measures direct and indirect effects and cannot distinguish between the two – so captures a wider impact of the virus.

Five year average weekly deaths by place of death, occurring between 2015 and 2019: Here.

The excess deaths are likely an underestimate due to the weekly death rate in 2020 between February until the start of the crisis in March being 5.8 ± 1.4 % lower than the five year average weekly death rate for this time of year. This leads to an overestimation of the expected deaths and hence an underestimation in the excess deaths.